216 



structure of these roots, and found that they very much resembled 

 the vertically growing pneumatophores of which I have men- 

 tioned the anatomy in my earlier paper (1. c. p. 87). 



As is well known, the pneumatophores of Avicennia and Lagun- 

 cularia have horizontal roots, creeping close below the surface of 

 the mud. On the gravelly clayish shores of the Hurricane Island, 

 in the harbour of St. Thomas, I succeeded in digging up some 

 voung Avicennia of which fig. 11 represents a plant in ^/s nat. size. 



Fig. 9. Avicennia nitida with aerial roots. From Great Cruzbay, St. Jan. 



(F. B. phot.) 



The figure shows how, from the base of each pneumatophore, a 

 vigorous food-supplying root emerges descending into the mud. 

 and besides the root itself, has several larger or smaller suckers. 



On a still drier soil, and at a longer distance from the sea, 

 Laguncularia occurs, often forming quite forest-like associations. 

 Thus on the north side of St. Croix below "Blue Mountain", in the 

 neighbourhood of the plantations "Rust op Twist" and "La Vallee", 

 on old lagoon substratum, we have a regular forest of Lagun- 

 cularia (fig. 12) with rather thick trunks, 40—50 feet in height. 

 The grayish humid soil is a sticky, clayish mass of rather firm 



